This proposal focuses upon the mechanism of action of a novel Arabidopsis protein, WVD2, that is involved in regulation of anisotropic cell expansion and responses to mechanical stimulation. WVD2 is predicted to form a coiled-coil structure, and may regulate growth and environmental responses by affecting cytoskeletal organization. Though WVD2 does not share significant sequence homology to proteins of known function, it does show compositional similarity to SCG10-1ike proteins involved in neuronal development and microtubule depolymerization. SCG10 and SCG10-1ike proteins have been implicated in human disease processes, neural plasticity, degeneration, and aging. Analysis of WVD2 has also enabled identification of related plant proteins containing a conserved domain designated the "KLEEK region". Many of these KLEEK-containing proteins are also predicted to form coiled-coils. This research will elucidate the molecular mechanisms by which WVD2 regulates anisotropic cell expansion, spiralization, and mechanosensing, and will define the biological functions of other KLEEK-containing proteins in Arabidopsis thaliana and other plant species. This will be accomplished by identifying proteins interacting with WVD2 using affinity chromatography and the Tandem Affinity Purification (TAP)- tag protocol, assessing the biochemical nature of interactions between WVD2 and cytoskeletal elements, performing structural analyses on purified recombinant WVD2, using molecular biological and bioinformatic approaches to identify additional KLEEK-containing and KLEEK-related proteins in other organisms, and analyzing the biological role of a KLEEK-like protein in the moss Physcomitrella patens.